1. Muscles of the Arm and Hand
PSK 4U
Mr. S. Kelly
North Grenville DHS

2. Biceps Brachii Origin: scapula
Insertion: radius, fascia of forearm (bicipital aponeurosis)
Action: supination and elbow flexion
Innervation: musculocutaneous

3. Brachialis Origin: humerus Insertion: ulna
Action: elbow flexion (assists biceps brachii by instigating this movement)
Lies deep to biceps brachii
Innervation: musculocutaneous, radial

4. Triceps Brachii (long, medial, and lateral heads)
Origin: scapula and posterior humerus
Insertion: proximal posterior ulna
Action: elbow extension; shoulder extension and adduction (when elbow is extended)
Innervation: axillary, radial

5. Forearm Muscles: acting on elbow, wrist, and finger joints
Flexor-Pronators
Extensor-Supinators
Originate via a common flexor tendon from medial epicondyle of humerus (common flexor origin)
Originates via common extensor tendon from lateral epicondyle of humerus (common extensor origin)

6. More on the Forearm
3 layers of muscles: deep, intermediate, and superficial
A layer of fascia separates deep layer of muscles from intermediate and superficial
Flexor retinaculum, aka transverse carpal ligament: roof of the carpal tunnel
Flexor tendons and median nerve pass through the carpal tunnel
FR increases effectiveness of tendons by preventing bowstringing, changing direction of forces when necessary

7. Supinator
Origin: lateral epicondyle of humerus, ulna, radial collateral ligament
Insertion: proximal 1/3 of radius
Action: prime mover in supination of forearm (aided by biceps brachii)

8. Pronators Pronator Quadratus Pronator Teres
Origin: distal anterior ulna
Insertion: distal anterior radius
Action: prime mover in pronation of the forearm (assisted by pronator teres)
Innervation: median
Origin: common flexor tendon, proximal ulna
Insertion: lateral radius
Action: pronation of forearm, weak elbow flexor
Innervation: median

9. Pronators

10. Flexor Digitorum Profundus
Origin: ulna, interosseus membrane
Insertion: phalanges, after penetrating tendons of FDS
Action: flexes fingers 1-4
Innervation: anterior interosseus, ulnar

11. Flexor Policis Longus Origin: radius, interosseus membrane
Insertion: distal phalanx of thumb
Action: thumb flexion
FPL is unique to humans: not present (or does very little) in other primates

12. Flexor Digitorum Superficialis
Origin: ulnar collateral ligament of elbow, CFO
Insertion: intermediate phalanges of 4 fingers
Action: flexes PIP, MP, wrist joints
Innervation: median

13. Palmaris Longus Absent in about 14% of population
Absence does not affect grip strength
Disadvantage: absence means lack of popular source for tendon graft
Test: touch pads of thumb and 5th finger + flex wrist… 2 or 3 tendons?

14. Brachioradialis Origin: lateral humerus
Insertion: styloid process of radius
Action: a flexor that also works to pronate AND supinate (in supination, it pronates as it flexes, and vice versa)
Innervation: median

15. Abductor Policis Longus
Origin: ulna, radius, interosseus membrane
Insertion: 1st metacarpal, trapezium, abductor policis brevis tendon
Action: abduction of thumb, keeps trapezium stable with APB
Innervation: radial

16. Extensor Digitorum Originates on lateral epicondyle
Inserts on medial 4 digits
Extends phalanges and wrist joint
Insertion splits on 4 digits to medial and lateral sides.

17. Anatomical Snuff Box Extensor policis longus tendon (posterior border)
Anterior (lateral) border: extensor policis brevis and abductor policis longus
Skeletal components: scaphoid and trapezium
Importance: blood supply of scaphoid is retrograde, therefore proximal fractures require attention to prevent necrosis
Name: comes from the practice of placing powdered tobacco on this surface for sniffing. Don’t ask why…

18. Primary Hand Grip Muscles (identification only)